Defroster for refrigerators



July 16, 1935. w, RUFF 2,008,628

DEFROSTER FOR REFRIGERATORS Filed Sept. 3, 1930 2 Sheets-Sheet 1 35 Q1 Eow Gttorncp July 16, 1935. A. w. RUFF DEFROSTER FOR REFRIGERATORS Filed Sept. 3, 1930 2 Sheets-Sheet 2 a Zhmcntor @Yon 5o Q 3. QRMFF Gttorncgs Patented July g STATES mm:

DEFBOSTER FOR BEFRIGEBATORS Alonzo W. Rufl, York, as, assignor to York Ice Machinery Corporation, York, Pa., 9. corporatlon of Delaware Application September a, 1930, Serial No. 479,542

25 Claims. (01. 62-115) The present invention relates to defrosting eral controls being shown and a refrigerating evaporators, and more particularly to smaller cabinet having therein an evaporator provided types of evaporators such as are used in conwith an electric heating element disposed in the nection with refrigerator cabinets for butchers, lower header ofthe evaporator.

grocers and restaurants. The problem of de- Fig. 2 is an elevation of a modified arrange- 5 frosting evaporators in small installations prement of evaporator and heating element, the sents serious difficulties in-that the evaporators latter being wound on the lowest coil of the are small and the evaporation of refrigerant evaporators; and therein is sluggish. Various means have been Fig. 3 is another modification of the invention proposed heretofore for introducing external heat in which the heating element is disposed in the o to the refrigerated space, all of which are obleg of thesuction trap. jectionable because the refrigerator is heated Referring to the drawings, the refrigerating up unnecessarily and is out of use for long pesystem comprises the usual compressor Ii driven riods of time and also because inexperienced by a motor i2, the condenser I3 and evaporator 16 operators often heat up the evaporator to such coil H. The system illustrated is one of the an extent that excessive pressures occur. It is flooded type and includes a suction trap 15 as likewise impracticable to apply the "hot gas well as a float chamber Hi. In practice, the method of defrosting to small refrigerators havevaporator comprises several coils l4 arranged ing only one or two evaporators connected to in parallel relation between an upper or gas 20 the suction of the compressor in series, there header l1 and a lower or liquid header l8, the being no evaporation and consequently no gas latter being in communication with the suction discharge from the compressor for use in the trap through a leg l9 and having an oil drain 2|. evaporator. In fact, it is desirable to defrost The compressor motor receives its current from the evaporators of small installations when the a source of electric energy designated 22 from compressor is closed down so that no high preswhich the heating element 23 is also supplied 25 sure gas is available. with current. A switch 24 permits the operator It has been found that the application of heat to connect either the motor or the heater with to the evaporator itself by means of an electric a power line circuit or to open the circut enheating element defrosts the evaporator coil tlrely. Interposed between the source of our- 80 evenly and quickly without appreciably heating rent and switch 24 is an excess pressure switch up the refrigerator cabinet or rendering it use- 25 responsive to pressure in the discharge line less during the defrosting period. 26 of a compressor and adapted to open the It has further been determined that an eleccircuit to stop the compressor when a predetric heater preferably submerged in the refrigtermined pressure in the discharge line has been r erant evaporates the refrigerant quickly and the built up. A similar excess pressure switch 21 gas thus given off condenses in the evaporator, is connected with the suction line 28 of the com the heat evolved by condensation melting the pressor, this switch responding to pressures refrost. This can be accomplished in a relatively Sulting from ap at n f th r fri ant durshort length of time and as a consequence little s application of heat thereto and interdllptrise in temperature results therefrom. ing the heater circuit when a predetermined 40 The present invention provides for heating the pressure in the evaporator has been attained. evaporator by an electric heating element, pref- It will be understood, of course, that the comerably a coil submerged in the refrigerant and pressor is inoperative while the heating circuit adjacent the bottom of the evaporator. Control is closed. Still another control device comprises devices responsive to temperature changes in the a thermostatic switch 29 mounted within the refrigerant and to pressures in the discharge and refrigerator cabinet 3| and in series with the suction lines of the compressor are associated motor l2. The thermostatic switch is set for with the motor and heating element to connect high and low limits, thereby to control operation and disconnect the motor or heater when cerof the compressor and maintain the proper temtain predetermined conditions exist. perature in cabinet 3|. V

The invention will be understood from the fol- If desired, an automatic -D valv 32 m y lowing description taken in connection with the be employed as a further measure of safety, the

accompanying drawings, in which valve being designed to respond to pressures above Figure 1 is a diagrammatic illustration of one those for which safety switch 25 is intended to form of the present system, the motor and sevrespond.

When it is desired to defrost the evaporator coils the switch 24 is thrown over to close the heater circuit. The refrigerant in the evapm rator is thus heated by the heating element 23 submerged in the refrigerant within the lower header of the evaporator. The position of the heater, above the lower end of the leg I! and at or near the bottom of the evaporator coil, is such that the vapors evolved by heating the liquid refrigerant are constrained to flow through the evaporator toward the suction trap and in so doing are condensed within the coil. The heat resulting from condensation in turn melts the frost on the coil. At the same time the liquefied refrigerant flows by gravity to the bottom of the evaporator in a more or less heated condition, the temperature and corresponding pressure being relatively high during the defrosting period. Uniform distribution of heat over all parts of the evaporator in a relatively short period is thus obtained.

In the modification shown in Fig. 2 the heating element comprises a winding surrounding the lowest coil of the evaporator. Heat is transmitted to the refrigerant through the coil causing circulation of the refrigerant by the resulting evolution of gas in the coil. Defrosting is accomplished in much the same manner as that described with respect to Fig. 1.

Fig. 3 illustrates still another arrangement wherein the heating element lies within the leg i9 connecting the suction trap with the liquid header 18. In this form of the invention the refrigerant is constantly warmed and circulated through the coil to melt the ice formed on the exterior of the coil.

While several forms of the invention have been illustrated and described herein, it is not intended that the specified arrangements limit the invention to what has been shown in the drawings.

What is claimed is:

1. In a refrigeration system, an evaporator; a defroster for said evaporator comprising means for applying heat to a portion of said evaporator; and means responsive to a predetermined pressure in said evaporator for interrupting the application of heat thereto.

2. In a refrigeration system, an-evaporator; a defroster for said evaporator comprising means for applying heat to the lowermost portion of said evaporator; and means responsive to a predetermined pressure in said evaporator for interrupting the application of heat thereto.

3. In a refrigeration system, an evaporator; a defroster for said evaporator comprising an electric circuit; an electric heating means in said circuit for applying heat to a portion of said evaporator; and means responsive to a predetermined pressure in said evaporator for interrupting said circuit.

4. In a refrigeration system, an evaporator; a defroster for said evaporator comprising an electric circuit; an electric heating means in said circuit for applying heat to the lowermost portion of said evaporator; and means responsive to a predetermined pressure in said evaporator for interrupting said circuit.

5. -In a refrigeration system, an evaporator; a defroster for said evaporator comprising means within the evaporator and submerged in the refrigerant for applying heat to the refrigerant.

6. In a refrigeration system, an evaporator; a defroster for said evaporator comprising electric heating means within the evaporator and submerged in the refrigerant for applying heat to the refrigerant.

7. In a refrigeration system, an evaporator; a defroster for said evaporator comprising means within the evaporator and submerged in the refrigerant for'applying heat to the refrigerant; and means responsive to a predetermined pressure in said evaporator for interrupting the application of heat thereto.

8. In a refrigeration system, an evaporator; a. defroster for said evaporator comprising an electric circuit; an electric heating element in said circuit and submerged in the refrigerant for applying heat to the refrigerant; and means responsive to a predetermined pressure in said evaporator for interrupting said circuit.

9. In a refrigeration system, an evaporator having upper and lower headers; a defroster for said evaporator comprising means within the lower header and submerged in the refrigerant for applying heat to the refrigerant.

10. In a refrigeration system, an evaporator having upper and lower headers; a defroster for said evaporator comprising means within the lower header and submerged in the refrigerant for applying heat to the refrigerant; and means responsive to a predetermined pressure in said evaporator for interrupting the application of heat thereto.

11. In a refrigeration system, an evaporator having upper and lower headers; a suction trap; means for connecting said headers with the suction trap; and means within one of said connections and submerged in the refrigerant for applying heat to the refrigerant.

12. In a refrigeration system, an evaporator coil; and a defroster for said coil comprising an electric heating element surrounding and in contact with the lowermost portion of said coil for applying heat thereto.

13. In a refrigeration system, an evaporator having liquid and gas headers; a conduit formmg a communicating passage between said headers and spaced from the evaporator; and a defroster comprising heat applying means in said passage.

14 In a refrigeration system, an evaporator having liquid and gas headers; a suction trap having a connection with each of said headers; a defroster for said evaporator comprising heat applying means in the connection between the liquid header and said suction trap for heating liquid refrigerant, said heat applying means being so disposed in said connection that vapors resulting from application of heat are constrained to flow through the evaporator.

15. The method of defrosting the evaporator of a refrigeration circuit connected to liquid and gas headers which comprises applying heat to liquid refrigerant locally and within the liquid header.

16. The method of defrosting the evaporator of a refrigeration circuit having supply and suction connections with a compressor which comprises suspending the fiow of the refrigerant through the evaporator and applying heat directly to the refrigerant internally of and near the lowermost portions of the evaporator.

17. The method of defrosting the evaporator of a refrigeration circuit which comprises generating heat within the volatile refrigerant in the evaporator to vaporize a portion of the refrigerant, while retaining substantially all the refrigerant in the evaporator.

18. The method of defrosting the evaporator of a refrigeration circuit which comprises applying heat locally to volatile liquid refrigerant in the evaporator at substantially the lowest point in the evaporator to vaporize the refrigerant, while retaining substantially all the re-, frigerant in the evaporator.

19. The method of defrosting the evaporator of a refrigeration circuit which comprises suspending the fiow of refrigerant through the circuit and applying heat directly to the refrigerant internally of and near the lowermost portion of the evaporator.

20. In a refrigeration system, an evaporator; and a defroster for said evaporator comprising an electric heating element contacting the lowermost portion of said evaporator'for applying heat thereto.

21. A refrigeration system including a compressor and an evaporator; an electric motor for driving said compressor; a defroster for said evaporator comprising an electric heating element; and means for selectively energizing the motor and the heating element.

22. A refrigeration circuit including an evaporator and means for circulating refrigerant through the circuit; an electrical circuit including means therein for operating said circulating means; a defroster comprising a second electrical circuit having a heating element therein; and means for selectively closing said circuits.

23. A refrigeration circuit including an evaporator and means for circulating refrigerant through the circuit; means for heating said evaporator to defrost the same; and means for selectively actuating the circulating means and the heating means.

24. In a refrigeration system, an evaporator containing volatile refrigerant; a defroster for said evaporator comprising means for applying heat locally to the refrigerant; and means responsive to a predetermined physical change of the refrigerant in the evaporator for interrupting the application of heat thereto.

25. In a refrigeration system, an evaporator containing volatile refrigerant; a defroster for said evaporator comprising an electric circuit; an electric heating means in said circuit for applying heat locally to the refrigerant; and means responsive to a predetermined physical change of the refrigerant in the evaporator for interrupting the application of heat thereto.

ALONZO W. RUFF. 

